1. Field of the Invention
This disclosure relates to telecommunications, and, more particularly, to systems and methods for handling data rate changes within a packet or frame.
2. Description of the Related Art
A wireless network is a type of telecommunications network whose interconnections are implemented using radio-frequency (RF) signals. In these systems, transfer of information is typically accomplished through a modulation process. At a transmitter, a modulator combines a data signal with a carrier wave and the resulting modulated signal is transmitted. Then, at a receiver, an RF stage detects the modulated signal and a demodulator extracts the data signal from the carrier wave.
The modulation process works by modifying the amplitude, frequency, and/or phase of the carrier wave as a function of the data signal. Certain modulation schemes (M-ary modulation) may use orthogonal waveforms to communicate two or more bits at once (i.e., as a single “symbol”), which effectively results in higher data rates. For example, a 4-FSK modulation scheme (i.e., a 4-level scheme) is capable of communicating two bits at once (i.e., a two-bit symbol). Meanwhile, an 8-FSK scheme (i.e., an 8-level scheme) is capable of communicating three bits at once (i.e., a three-bit symbol). Therefore, under similar conditions, a signal transmitted with an 8-FSK scheme has a higher data rate than a signal transmitted with a 4-FSK scheme. However, changing the modulation scheme during the course of a transmission typically requires an expensive resynchronization process.